U.S. Patent publication 2004/0231808 relates to a folding grille assembly to be used to close an opening in a narrowing wall. The grill assembly has a pocket and a folding grille. The pocket is adapted to be mounted on one side of the opening aligned with the wall and forming part of the wall. The folding grille has a plurality of narrow, vertical, panels, the panels hingedly joined together in serial fashion by vertical hinges. Every second panel only carries a vertical mounting rod at its top end extending up from the top, center of the panel, and every second mounting rod only carries a trolley by means of which the grille can be movably supported at the top opening of the grille. The pocket forms a receptacle for the grille when the grille is folded to open the opening.
US Patent publication 2008/0188175 relates to a recirculating fan, for installation in an upper region of a building space, and having, a housing, a fan, an air vent ring defining an intake path and a discharge path, an air grille for intake and discharge paths, the air grille being releasably attached to the housing and being moveable relative to the housing, and releasable fastening devices for releasably fastening the air grille to the housing.
U.S. Pat. No. 7,566,263 relates to a combination of a grille and a connector frame for a duct outlet in an HVAC system. At least one lock element extends from one of the connector frame and the grille and releasably engages the other of the connector frame and grille in a releasable connection to hold the grille to the connector frame. The lock element may be manipulated from the exterior of the grille to release the grille from the connector frame without the use of tools.
US patent publication 2007/0056229 relates to a fastening means of an air grille including a grille face, a filtering device, a stationary frame and door latches, in which the grid face is hinged to the stationary frame with one side, and the opposite side of the grid face is fastened on the stationary frame with the door latches. The door latches molded of plastic are located on the grid face in movable connection with a catching hook at the middle portion. A pushing portion is built upon the upside of the door latch, and a L-shaped catching shoe on the lower portion. Above the L-shaped catching shoe, the catching hook is built up for holding the grid face on, and an open slot constructed of the low leg of the L-shaped shoe and the bottom of the pushing portion is used to catch on the stationary frame. When opening the grid face, just need to push the door latches respectively to outward so as to slide off from the stationary frame, then the grid face is opened wholly; in this case, locking or opening of the grid face to install or remove the filter becomes easier.